I have dense breasts, a physiological fact that was neither here nor there until July 25.

That’s the day I turned 40, which consequently marked the day I was supposed to start paying close attention to my breasts. They’ve served me well, nourishing three kids and ensuring my tops fit the way they should. But they’d suddenly become suspect, literally overnight.

Barring a family history of breast cancer, a woman’s 20s and 30s are typically carefree, breast-wise. Do your self breast exam (I do) or don’t in those years — there are differing opinions on this — but celebrate your 40th, and women are suddenly plunked into the incredibly confusing and contradictory world of screening mammography.

It wasn’t always this complicated. Until 2009, 40 marked the age at which women were supposed to start scheduling their annual screening to see whether their breast cells had turned traitor. But three years ago, the U.S. Preventive Services Task Force (USPSTF) upended the guidelines and advised women to wait until 50 — and to get mammograms only every two years until age 74. Meanwhile, the American Cancer Society and the American College of Radiologists advocate sticking with the long-time recommendation to begin yearly screening at 40.

And with that, an entire decade of women ages 40 to 49 has been thrust into diagnostic limbo. To screen or not to screen: that is the question.

It’s maddening to try to make sense of the data, a mass of contradictory research that feels like a medical point-counterpoint. It would be borderline amusing if our health was not at stake.

It hardly helps that conflicting studies are coming out all the time, including one this week that found that up to 20% of breast cancers among women in their 40s could be missed under the new USPSTF guidelines. On the other hand, the analysis the USPSTF relied upon found that screening women in their 40s can lead to false positives, overtreatment and more risk than harm. Last week, a much talked-about report in the New England Journal of Medicine concluded that the benefits of screening mammograms are not worth the risk of potentially unnecessary follow-up tests because mammograms simply aren’t very good at detecting aggressive cancers early enough to change the course of disease. In the past 30 years, the authors estimate that 1.3 million U.S. women were overdiagnosed with breast cancer — that is, they endure the emotional scare of a false positive finding, along with unnecessary biopsies, tests and surgeries, or they were treated for tumors that would not have gone to become a problem. In fact, in 2008, the authors figure that a full third of breast cancer diagnoses fell into that category. In one commentary on the study, Dr. Val Jones writes :

A question on most women’s minds (as they turn 40 and beyond) is whether or not they should get a screening mammogram (x-ray of the breasts)… Even though it makes intuitive sense to be screened, long term observations confirm that overall, mammograms do more harm than good.

Contrast that with the views of Dr. Elizabeth Arleo, an assistant professor of radiology at New York–Presbyterian Hospital/Weill Cornell Medical College, who led this week’s study that found that close to 19% of cancers picked up by screening mammography were found in women in their 40s.

“It seems unacceptable to potentially miss nearly 20% of the breast cancers we are identifying,” Arleo said in a statement. “This, in our view, would represent a substantial degree of underdiagnosis.”

Stating the obvious, Arleo observed that “the inconsistent information is very confusing for everyone.”

It’s enough to drive women crazy. And it gets even more convoluted if you factor in something called breast density, which can be determined only through mammography. The denser the breast, the more connective tissue; the least dense breasts have the most fatty tissue. Young women typically have denser tissue, which often becomes fattier over the years. And both dense breasts and tumors show up white on a mammogram, making it harder to distinguish between normal findings and cancer. The Dr. Susan Love Research Foundation characterizes the challenge as “akin to looking for a polar bear in the snow.”

Does that mean we shouldn’t give a darn about our density? Judging by new legislation, five states hardly think so. New York, Virginia, Texas, California and Connecticut have all passed laws requiring that mammogram reports inform women of their breast density levels. Communicating breast density to women can allow them to consider whether to pair a mammogram with an ultrasound for enhanced detection.

Connecticut was first to sign, after being prompted by Nancy Cappello, a retired educational consultant who found out she had dense breasts only after she was diagnosed with advanced breast cancer in 2004 at the age of 51. Two mammograms had showed nothing; Cappello was tipped off after her doctor felt a thickening, which was then spotted on an ultrasound. “I did everything right,” says Cappello. “I had my yearly mammograms. And then I found out that so many women have dense breasts like me.”

Cappello, who launched a website called Are You Dense, recommends discussing with your doctor the pros and cons of mammography and the potential benefits of ultrasound for women with dense breasts. (Women with dense breasts should also seek out the higher resolution of digital mammography. And those women with a family or genetic history of breast cancer should look into getting supplementary MRIs.) But in truth, the message to talk to your doctor may only muddle things further. Physicians have very different opinions on what the correct approach is. Most agree that mammography is an imperfect screening tool. Despite that, some believe that women should keep their annual appointments until something better comes along. Others think exactly the opposite.

A physician’s role is to lay out the data and the potential risks and benefits, says Dr. Julie Gralow, director of breast medical oncology at the University of Washington and Seattle Cancer Care Alliance. Every doctor will do that differently. Gralow, for one, disagrees with the recommendation to wait until 50 to start getting mammograms. While she acknowledges that screening mammography probably finds some early cancers that might never need treatment, she believes the upside of catching cancer so early that a woman could avoid chemo or opt for a lumpectomy rather than a mastectomy is worth the trade-off. Furthermore, we just don’t know which cancers will end up killing. “Finding cancer early has benefits,” she says. That said, she empathizes with the anxiety that accompanies false positives. “I’ve had three breast biopsies myself,” she says. “I get it.”

Still in the dark about whether to start screening at 40? You might check out this tool that assesses breast cancer risk. Then, while your mind is whirling with this study and that recommendation, spend a few minutes pondering what’s getting lost in this whole conversation: the misplaced emphasis on screening rather than prevention. Exercise, lose weight if you need to, eat healthy — and maybe one day, the dilemma over when to start screening might not be quite as pressing.

During my own experience of breast cancer I discovered many secrets that we are not told. I realized how much the health care system spins what little information it reveals to us through mainstream media. In fact, even the term "save your life" carries a different meaning from the way we "laypersons" use it.

The story I wrote about my experience and research is posted at http://mammogramsanddcis.blogspot.com (mammograms and dcis). If you read it, you will understand how this matter is all about costs. You will also see why having a mammogram only every 2 years is a very risky idea. For one thing, by the time calcifications--the first indicator of the most common type of breast cancer--show up, the cancer has already been there for 8-10 years or more. What it does during that time is a matter of happenstance. In 6% of all breast cancer cases, there is already lymph node involvement at the time of diagnosis. Even one involved node means that cancer cells are being carried to other parts of your body. It automatically means chemotherapy and automatically shortens your life expectancy. There is much that we are not told, including about the use of the better tool of contrast MRI screening.

I was almost 47 when mammography found my breast ca. If I had waited until I was 50 to start I have no doubt I would not be writing this comment. I have had 2 subsequent biopsies and I am extremely proactive about early detection. I have tossed around the idea of Thermography I need to research this more. I work "in breast cancer" and I understand the controversy surrounding all of it including the lobbying insurance companies whose bottom line is the dollar sign. I ask myself how many woman would have died by now if we did not have mammography at all, if all we had was self-esam? It seems no one addresses that.

Science is not black and white. Knowing the facts about the advantages and disadvantages of mammograms doctors and patients together can make their decisions how to go about having mammograms or not or how often. Also if there is a detected problem how to deal with it. Learn what you can about preventing, detecting and treating breast cancer and based on that info make your own decision. Scientist in the mean time work hard to get better, more accurate diagnosis and to find cure.

I choose quality of life over the tiny chance I'd get an increase in quantity through screening. I take great care of myself and accept that nature will takes its course, but each woman needs to understand the current state of the science and make a decision for herself.